1. Field of the Invention
The present invention relates to a process for eluting egg white lysozyme from a weakly acidic cation exchange resin having egg white lysozyme adsorbed thereon.
2. Description of the Prior Art
As one process for extracting from egg white lysozyme which is known as a bacteriolytic enzyme present in the egg white in trace amounts, it has previously been proposed to cause a weakly acidic cation exchange resin such as Amberlite, Duolite or Diaion to adsorb the lysozyme and then to elute the lysozyme therefrom. Ordinarily, the lysozyme is eluted from the resin by a method which involves first packing the resin having the lysozyme adsorbed thereon in a column, and thereafter eluting the lysozyme with a salt solution having a pH substantially in the neutral range, e.g., of the order of 6.5 to 7.5, such as an aqueous solution of sodium chloride or ammonium secondary phosphate as is disclosed, for example, in Japanese Patent Pub. No. 7828/1966. The salt solution includes, in addition to a solution obtained by simply dissolving a salt in water, a so-called buffer solution obtained by admixing a salt with an acid or an alkali having either one of the ions constituting the salt (anion or cation).
However, the column method, while ensuring process efficiency due to a continuous operation system, cannot effectively promote intimate contact between the resin having lysozyme adsorbed thereon and the salt solution and thus is unsuitable especially in the case where the resin to be treated is in only a small quantity. For this reason, a batch process is preferred in order to elute lysozyme effectively from a resin having lysozyme adsorbed thereon.
However, when a salt solution of a pH value near the neutral range is actually used in a similar manner for eluting lysozyme from a resin by a batch process in accordance with the elution process described above, it is difficult, even when the elution operation is repeated several times and the lysozyme is collected from each of the eluates thus obtained by a step such as salting out, to increase the recovery, i.e., the yield, in spite of the troublesome elution operation repeated several times. Presumably this is because the concentration of the lysozyme in the eluate has become lower. A solution for this problem has long been sought, but has not been found to date.
As a result of our extensive research, it has been found that, in the above described batch process for eluting egg white lysozyme adsorbed on a resin by contacting the resin with a salt solution, the lysozyme can be eluted more effectively by adding an alkali agent to the eluate containing the resin having lysozyme adsorbed thereon.